The closes one is at Knott's Berry Farm. There's also one in Irvine, unless it has closed. I think it was due to close sometime. Unfortunately, I haven't been to either one. But they usually have a place just for little kids.
Wild Rivers is in Irvine, the lease has been extended and it is not closing. It's the one I would chose for the day. They have a whole area dedicated to little ones, plenty of fun for everyone.